As the title implies, I need help with programming in the shooting function for the space ship. I'm supposed to program a Space Invaders clone in good ol' pascal using non other than the CRT library; that means no graphics, just characters to interpret the game's graphics. As of now I managed to code-in the spacebar function to create the bullet, but what I want to do now is to move the bullet upwards.
Code:
USES crt;

CONST
	max_row = 40;  //Matrix dimensions
	max_col = 80;
    Spacebar = #32;

// Can_Shoot checks the posibility to shoot, not yet implemented
//	Shooting checks if the user y pressing the spacebar key 
PROCEDURE Bullet_Creation(var Can_Shoot : boolean; var Shooting : char);
BEGIN
REPEAT
        Shooting := readkey;
			IF Shooting = Spacebar AND Can_Shoot THEN
				BEGIN
                 gotoxy(9,9);

                 writeln('I');
                 Can_Shoot := false;
				END;
UNTIL keypressed;

END;

// Main Program
var Can_Shoot : boolean;
  Shooting : char;
  MATRIX : ARRAY[1..max_row,1..max_col] OF char;
  i,j : byte;
BEGIN
	Bullet_Creation(Can_Shoot,Shooting);


	//Print Matrix
  for i:=1 to max_row do
  begin
  for j:=1 to max_col do
   write (MATRIX[i,j]);
  writeln;
  end;

    readln();

END.
Thanks in advance!
Psycho.

PD: As you can see, the gameplay field is supposed to be a matrix.